FORT HOOD (AP) – Expert witnesses are expected to begin testifying in the case of the Army psychiatrist on trial for the 2009 shooting rampage that left 13 dead at Fort Hood.

The military court-martial against Hasan enters its fifth day of testimony Tuesday.

Hasan faces the death penalty if convicted of premeditated murder. He is also charged with attempted premeditated murder in the November 2009 attack that left more than 30 wounded.

So far, witnesses have described in gruesome detail how Hasan fired bullet after bullet into a crowd of unarmed soldiers, leaving bodies and blood in his wake at a building used for vaccines and other medical treatment.

Hasan is representing himself and has asked no questions of shooting victims. His standby attorneys have protested that Hasan is seeking a death sentence.